Defibrillator system

ABSTRACT

The invention provides a portable defibrillation system ( 2 ), including: a high voltage switch, and current control circuit ( 16 ) connectable to and fed by a power source ( 6 ); a high voltage transformer ( 14 ) fed by the current control circuit; a pair of electrode pads ( 12, 12′ ) connected to the high voltage transformer, and a computer-based controller ( 18 ), operationally connected to the current control circuit, for governing the application of current to the high voltage transformer and, in turn, to the electrodes, wherein the high voltage applied to a patient by means of the electrode pads is directly derived from the power source.

FIELD OF THE INVENTION

[0001] The present invention relates to intensive care systems for theearly treatment of sudden arrhythmias, and more particularly, to suchsystems which are suitable for domestic or outpatient use by non-medicalpersonnel, on a dying patient.

BACKGROUND OF THE INVENTION

[0002] Heretofore, sudden cardiac death caused by ventricularfibrillation or cardiac arrest, was the major cause of death among theadult population in developed countries. Ventricular fibrillation can behalted and normal heart activity restored, by the electricaldefibrillation procedure, comprising an electric shock applied to theheart. Similarly, heart arrest can be treated by pacing electricalsignals, that is, a pulse train, at the rate of 60-80 pulses per minute.The defibrillation procedure is usually effective when applied inintensive care units in hospitals, where a state of fibrillation iseasily detected and treatment is quickly applied. Hospital intensivecare units are usually equipped with expensive defibrillation equipment,along with professional personnel who are able to perform the treatment.

[0003] The above considerations also apply to the state of heart arrestand the use of an external pacemaker device. Thus, while the descriptionof the present invention relates to defibrillators, it should beunderstood that it is also meant to include pacemaker systems.

[0004] It is of paramount importance that a defibrillation procedure bedone immediately; otherwise, irreversible, irreparable damage is caused.The patient's brain is be damaged within minutes of the start offibrillation, due to a lack of oxygen supply, and all other organs willstop functioning. Early defibrillation restores cardiac function andspontaneous respiration, avoiding anoxic brain damage. In addition,there is a clear linkage between the elapsed time between the beginningof ventricular fibrillation, the beginning of the defibrillationprocedure, and the procedure's success.

[0005] The majority of potential fibrillation victims live at home,however, and are not under constant medical supervision. This is evenmore so with the modern trend towards treatment of patients at home.These people cannot be given immediate defibrillation treatment, forseveral reasons:

[0006] 1) From the moment that the victim of ventricular fibrillationloses consciousness, it will take at least from 10-20 minutes until themobile care unit reaches him. Therefore, in such cases defibrillation isusually not successful and irreversible cardiac damage is caused; if thepatient survives, he will remain in coma with permanent brain damage.

[0007] 2) Presently used defibrillation equipment is expensive, costingin the range of thousands of dollars. The majority of the people cannotafford to include such equipment as part of their home first aid kits.

[0008] 3) Much of the presently used defibrillation equipment must beoperated by professional, trained medical personnel, who diagnose thecase as fibrillation, find the right equipment, and use it correctly toapply electric shock at the proper location. Non-professional people areunfamiliar with such equipment; and moreover, they tend to panic and beineffective in an emergency situation. Therefore, family members andneighbors usually cannot be relied upon to perform defibrillationtreatment.

[0009] 4) The defibrillation equipment has to be kept in good operatingcondition so that it will be ready for use in an emergency. Hospitalmaintenance teams routinely keep all equipment in good condition andperform required periodical tests and repairs. It is difficult, however,to keep complex defibrillation equipment in good condition at home andto do the required testing and repairs.

[0010] 5) Defibrillation equipment may be dangerous if misused. Highvoltages generated by the equipment can endanger its operators,children, or other non-professionals. The existing equipment lacks thesafety devices which are required for home use.

SUMMARY OF THE INVENTION

[0011] It is therefore an object of the present invention to overcomethe above-mentioned problems and to provide a low-cost, automaticdefibrillation system utilizing available alternating current, fortreating fibrillation and cardiac arrest patients at home.

[0012] Thus, the invention provides a portable defibrillation system,comprising a high voltage switch and current control circuit connectableto and fed by a power source; a high voltage transformer fed by saidcurrent control circuit; a pair of electrode pads connected to the highvoltage transformer, and a computer-based controller, operationallyconnected to the current control circuit, for governing the applicationof current to the high voltage transformer and, in turn, to theelectrodes, wherein the high voltage applied to a patient by means ofthe electrode pads is directly derived from the power source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will now be described in connection with certainpreferred embodiments with reference to the following illustrativefigures so that it may be more fully understood.

[0014] With specific reference now to the figures in detail, it isstressed that the particulars shown are by way of example and forpurposes of illustrative discussion of the preferred embodiments of thepresent invention only, and are presented in the cause of providing whatis believed to be the most useful and readily understood description ofthe principles and conceptual aspects of the invention. In this regard,no attempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice.

[0015] In the drawings:

[0016]FIG. 1 is a block diagram of the defibrillation system accordingto the present invention;

[0017]FIG. 2 is a circuit diagram of a first embodiment of theinvention;

[0018]FIG. 3 depicts graphs showing the waveforms produced at differentpoints in the circuit of FIG. 2;

[0019]FIG. 4 is a circuit diagram of a second embodiment of theinvention;

[0020]FIG. 5 depicts graphs showing the waveforms produced at differentpoints in the circuit of FIG. 4;

[0021]FIG. 6 is a circuit diagram of another embodiment of theinvention, and

[0022]FIG. 7 depicts graphs showing the waveforms produced at differentpoints in the circuit of FIG. 6.

DETAILED DESCRIPTION

[0023] Referring now to FIG. 1, there is shown a block diagram of anautomatic defibrillation system 2 according to the present invention.System 2 is connectable, via switch 4, to a common power source 6, e.g.,AC mains outlet 8 or, alternatively, to a battery-operated DC-to-ACconverter 10, for use when mains power is not available.

[0024] System 2 includes a pair of electrodes 12, 12′ electricallyconnected to, and fed by, a high voltage output transformer 14, e.g., astep-up transformer, receiving power from source 6 via a high voltageswitch and current control circuit 16. The latter is governed bycomputer-based controller 18. Advantageously, measurement leads 19, 19′connect electrodes 12, 12′ to the computer-based controller 18. Thesystem may be optionally furnished with an audio-visual alarm 20 and anECG visual output manual operation unit 22.

[0025]FIG. 2 illustrates a first embodiment of the invention. System 2is connectable via switch 4 to the mains power source 6. A step-downtransformer 24 feeds a power supply 26, providing the required DCvoltage to the system. A zero cross detector 28 is connected to thelow-voltage side of transformer 24, and detects the exact timing of thezero crossing of the mains sine wave, to be used as a reference for theoperation of the system. A monostable 30, e.g., a 30 msec monostable, iseither manually triggered by push button 32 or automatically throughleads 34 to a computer (not shown) for analyzing the ECG signals of apatient. The computer is connected to a main gate synchronizer 36, whichsynchronizes between the input signals arriving from the zero crossingdetector 28 and the signals arriving from the monostable 30. The outputfrom main gate synchronizer 36 is fed to a positive half-cycle detector38, for detecting the beginning of a first positive half-cycle of themains occurring in response to manual or automatic triggering.

[0026] As a first part of the procedure for controlling the power thatwill be transferred through the output transformer 14 to the electrodes12, 12′, circuit 40 enables a time delay of, e.g., 0 to 5 msec, countedfrom the zero crossing of the sine wave. This delay marks the beginningof the pulse of energy transferred to the patient. The second part ofthe power-controlling procedure comprises generating a pulse ingenerator 42, e.g., 1 to 10 msec wide, according to the amount of energythat has to be transferred to transformer 14 and thence, via electrodes12, 12′, to the patient.

[0027] The high voltage switch and current control 16 can be dividedinto two components: IGBT control 16′, which transforms the logic levelsused in the other parts of the system to the levels required to triggerthe high current IGBT switch 16″. The latter is a high power switchsupplying the primary of high voltage transformer 14 with an adequatewaveform, shaped by pulse width generator 42.

[0028] Referring now also to FIG. 3, the system's waveforms are shown inalignment, including the mains waveform A, the zero cross output signalB, monostable 30 output signal C, main gate 36 synchronizing signal D,first positive half-cycle signal E, delay signal F, pulse width waveformG at the output of the pulse width generator 42, and the actual highvoltage output waveform H, which is applied to electrodes 12, 12′.

[0029] Thus, from the synchronized signal, the zero crossing pulsepreceding the first positive half-cycle is selected and used as atriggering signal for the generation of a pulse whose beginning timingand end timing can be controlled in order to ensure that the requiredamount of energy is transferred to the patient. This pulse is, in turn,used as a gating signal to the high current switch applying the mains'power to the step-up output transformer 14, used to obtain the requiredhigh voltage to be applied to the patient's chest.

[0030]FIGS. 4 and 5 depict a modification of the embodiment of FIGS. 2and 3, in which there is provided a high frequency generator 44 forproviding a train of high frequency (A, FIG. 5), e.g., a 12 to 24 KHzsinusoidal waveform B, to be used as a power source for the step-upoutput transformer 14. After passing through a wave shaper 46, thepulses are shaped as shown at H. The high voltage output applied to thepatient is thus shown as I of FIG. 5. The wave shaper 46 enables theapplication of consecutive pulses shaped according to the requirementswithin limits of less than 200 ms delay, in contrast with known systemsbased on capacitor discharge where it takes several seconds before asecond discharge is possible.

[0031] Furthermore, the wave shaper enables the application of pulsesshaped according to any requirements, within limits of the sine wave,having variable peak outputs and starting and stopping at will, creatinga mono or biphasic waveform, or continuous wave composed of two or moresegments, thereby enabling the delivery of the exact amount of energyrequired.

[0032] A further embodiment is shown in FIGS. 6 and 7. Accordingly, anexponential amplitude controller 48 is connected in circuit between themains and the output transformer 14. The controller 48 is used tocontrol the amplitude (A, FIG. 7) of the sinusoidal waveform obtained bythe mains (B, FIG. 7), resulting in a progressively reduced high voltagewaveform C. Amplitude decrease is calculated by the system in such a waythat the accumulated energy transferred to the patient reaches therequired value determined by the patient's condition and other, per seknown, considerations.

[0033] It will be evident to those skilled in the art that the inventionis not limited to the details of the foregoing illustrated embodimentsand that the present invention may be embodied in other specific formswithout departing from the spirit or essential attributes thereof. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. A portable defibrillation system, comprising: ahigh voltage switch and current control circuit connectable to and fedby a power source; a high voltage transformer fed by said currentcontrol circuit; a pair of electrode pads connected to said high voltagetransformer, and a computer-based controller, operationally connected tosaid current control circuit, for governing the application of currentto said high voltage transformer and, in turn, to said electrodes;wherein the high voltage applied to a patient by means of said electrodepads is directly derived from said power source.
 2. The portabledefibrillation system as claimed in claim 1, further comprisingmeasurement leads connecting said electrodes with said computer-basedcontroller.
 3. The portable defibrillation system as claimed in claim 1,wherein said power source is selected from the group consisting of amains AC power outlet and a battery-operated DC to AC converter.
 4. Theportable defibrillation system as claimed in claim 1, further comprisingan audio-visual alarm connected to said computer-based controller. 5.The portable defibrillation system as claimed in claim 1, furthercomprising an ECG visual output manual operation connected to saidcomputer.
 6. The portable defibrillation system as claimed in claim 1,wherein said computer-based controller is connected to said power sourcevia a zero crossing detector for establishing a system operationreference.
 7. The portable defibrillation system as claimed in claim 6,further comprising a main gate synchronizer connected to said zerocrossing detector and a patient's ECG signal.
 8. The portabledefibrillation system as claimed in claim 1, further comprising a waveshaper for shaping voltage pulses produced by said high voltagetransformer.
 9. The portable defibrillation system as claimed in claim8, wherein said wave shaper is capable of application of pulses with avariable peak output voltage facilitating delivery of an exact amount ofenergy required.
 10. The portable defibrillation system as claimed inclaim 1, further comprising an exponential amplitude controllerconnected in circuit between said power source and said high voltagetransformer.